The present invention relates to an exhaust apparatus and to monitoring means for such an exhaust apparatus. The monitoring means activate an alarm device, such as a light and/or buzzer any time when the filter of the exhaust apparatus requires cleaning or replacing.
Prior art monitoring devices for the operation of exhaust fans with filter means have the disadvantage that the increasing contamination of the filter means and thus the decreasing efficiency of the filter action cannot be ascertained with the desired precision and certainty. As a result, it is possible that the fan motor may be exposed to damaging speed increases due to load reduction and the suction efficiency and odor removal are reduced. For these reasons motor burn-outs in conventional exhaust fans cooperating with a filter are not uncommon.
In view of the above, it has been suggested heretofore to monitor the degree of contamination of a filter arrangement in an exhaust mechanism with the aid of a poppet or disk valve arranged to connect the atmosphere with the space between the filter device and the exhaust fan proper. Such a valve responds to the pressure difference in front of and behind the filter device and actuates a suitable signalling device when the valve opens in response to a predetermined, adjustable reference pressure to thereby indicate that the filter requires cleaning or replacement. However, such a pressure differential responsive valve is itself rather sensitive to contaminations. Therefore, a continuous maintenance is necessary for monitoring the valve. As a result, such valves are not very effective for the intended purpose.